To keep this topic somewhat relevant, the only black-box change the Hybrid Rendering team would need to make is to expose a fast-path for streaming individually unique proxy meshes without fragmenting ECS chunks. This other black-box piece is already in active development: Feedback Wanted: Streaming Virtual Texturing
The rest can be done with a custom SRP and more time and energy than I have. 
DOTS solves the problem of writing game code that runs fast enough to run alongside such a technology.